Overthinking sex and PMO, and it's impact on sex with gf

I wonder how much my overthinking has affected my relationship. Before, when I didn't know about NoFap, I never got moody, drained or anything after sex. I got calm and sleepy. After fapping, on the other hand, I felt like shit. I had problems with PMO, without ever thinking about it, and reading about others' situation made me see how much it might had impacted parts of my life.

Now, after digging in to this for 2 years, wondering if it has impact my libido, attraction towards gf and so on, sex drains me in the same way as PMO does. But as I said, it wasn't like that before and I'm still with the same GF. I feel good after sex and we often just lie in bed holding each other and talking. But after a while I feel anxious and moody. The next day I sometimes get this feeling of emptiness rushing over me.

After I started overthinking PMO, porn, sex, attractions etc, everything has become sexual. I think overthinking (great sentence, I know) can ruin absolutely anything. Things isn't ment to be overthought, because very few things are purely logic if you dig deep enough in to a matter. The problem is that I'm very good at overthinking everything.